There are a wide range of lifting and/or hoisting devices used in the industry which include both center-pull style devices and side-pull devices. These devices are used to lift a variety of heavy loads or objects, such as die sets and molds; however, the invention has much broader applications and may be used for a variety of applications where it is necessary to secure a ring to a structure, either to lift the structure or to hold down a structure such as containers, air crafts, air vehicles, boats, etc.
Through the years, a large number of hoisting devices have been developed which allow for a ring to be connected to the hook of a hoist wherein the ring pivots and swivels for the purpose of automatically adjusting the disposition of the ring with respect to the force being applied to the hoist during the lifting procedure. Such devices are found in patents incorporated by reference herein which will be discussed more below.
The center-pull hoist devices have a post assembly that allows 360-degree rotation of a support or body member. The rotating support member carries the load lifting ring, which can be in many forms include the form of a U-shaped clevis. The clevis pivots through a center clevis axis of the rotating support member and has a pivot arc of about 180 degree.
Like the center-pull style, the side-pull hoist ring includes a rotating support member mounted onto the load by a post assembly. In a side-pull hoist ring, the support member can be generally U-shaped to define an outer bite portion in which a circular load ring is pivotally mounted. The circular load ring is offset from the axis of the center post assembly.
These prior patents include the device shown in Schron Jr. et al U.S. Pat. No. 5,634,734 that discloses a center-pull style hoist device and is incorporated by reference for showing the same.
Fuller et al U.S. Pat. No. 6,652,012; Fuller et al U.S. Pat. No. 6,443,514; and Fuller et al U.S. Pat. No. 6,068,310 all disclose side-pull hoisting devices and are all incorporated by reference for showing the same.
All of these device disclose effective hoisting devices that have been used effectively in the industry for many years and which are merely provided as background for the invention of this application.
In addition to the above-described hoisting devices, also known in the patent art is a patent to Mueller U.S. Pat. No. 5,286,130, which discloses a clevis assembly. While the Mueller patent is possibly an effective device, it has many limitations and disadvantages that produce a less than ideal lifting device. In this respect, lifting devices are most effective if they are strong and durable and if they can smoothly and accurately secure and/or move a load that can be very heavy. Thus, it is important that the device smoothly and automatically adjust itself when loaded based on the movement of the load. Part of this is the ability to smoothly rotate about the stud or post axis. As is shown in the drawings, Mueller's device includes a fastener 18 having a round cylindrical head portion 18a and a shank portion 18b defining a threaded lower end 18c. Head portion 18a has a length or height slightly less than the height of recess 10e and is sized to be journalled in recess 10e. Shank portion 18b has a diameter slightly less than the diameter of the inner periphery 16d of collar 16 so that the shank portion may pass loosely through the collar to position the threaded lower end 18c of the fastener below the clevis. The threaded engagement between collar 16 and head portion then support the fastener within the recess of body 10. As a result, the friction between the head and the collar makes rotation of the body about the fastener based on metal-on-metal contact that can prevent rotation or at least make rotation difficult and/or non-smooth. In addition, the more torque used to tighten the Mueller hoist, the more friction that will be present between the bolt head and the collar thereby making the rotation of the shackle about the bolt access more restricted. Further, Mueller relies on a threaded collar to support the weight of the load and this collar could loosen over time by the weight and rotation of the load.
In addition, Mueller utilizes a fastener that is completely encased within the body of the clevis assembly wherein the bolt cannot be turned to tighten his device. Conversely, Mueller must utilize a set screw 24 and brass bushing 26 to frictionally engage his bolt head and then the entire assembly must be rotated to tighten fastener 18 into a threaded hole. As can be appreciated, this must be done by hand and a torque determining devices, such as a torque wrench, cannot be used to determine if a desired torque between the clevis assembly and the load has been achieved. However, if the set screw is tightened against bolt head 18a, the clevis assembly cannot rotate. As a result, the set screw must then be backed off if his device is to be allowed to rotate about the bolt axis. Nonetheless, Mueller is incorporated by reference as background material.
Similarly, Mueller U.S. Pat. No. 3,492,033 discloses a design that includes metal-on-metal contact to allow for the rotation of the device about the stud or post and support the load. And, this arrangement requires the use of the threaded collar to support the post within the body. This Mueller patent is also incorporated by reference as background material.